You don't say which motor/model yours is.
If you're looking for original look tires, then the factory tire spec for 914/4's was:
1.7 & 1.8L cars: 165(/80)SR15 ... "S" Speed rating & "80" or +/-80% ht-to-width profile
2.0L cars: 165(/80)HR15 .... "H" Speed Rating
There should be a tire size & inflation sticker on your gas tank's expansion tank - next to the filler.
"T" speed rating wasn't around then, but modern 165(/80)TR15's would work for any motor, since the T's 118 mph rating matches the spec top speed for 2.0's, & realistically you can use a 165SR15 on a 2.0 for DD & if you're not trying to drive 118 mph for hours on end.
Bridgestone used to make a 165TR15 up to a couple of years ago, but don't know who else. Vredestein & Michelin make 156SR15 & 165HR15 tires still, which are handled by Coker & other vintage tire suppliers. You might try Lucas Tires in Long Beach CA & Ohio somewhere for a better price on these, as well as checking a google shop search by tire size, since "new" suppliers & brands may come up.
In the early 1990's the factory sent out an advisory letter to use the 195/65R15 in "S" or "H" ratings on 914s (T's came later), after the 165s disappeared from the market. The early 195s in the late 70's & early-`80's were too tall & rubbed at full turn - as noted above on the 205's.
I wouldn't use anything tire-wise larger if they rub myself, cuz you're going to rub off paint & expose bare metal to rust, &/or cut the sidewalls on the exposed edge of the wheel well cutouts on the outer fenders, &/or cause damage to your steering rack/suspension - depending on what it's contacting to rub. Some folks also get rub at the top of the rear well cutouts.
195/65(S-H-T)R15 are available from a number of common tire sources like Tire Rack, but you may be better off going to a local shop that will work with you to mount some trial tires to let you check for rubbing in an actual test drive, to get the best fit on your 914.
195/65R15 will give you a speedo & odometer error of 8% IIRC (see the tire size calculator at the 914 Info section's button at the top of this webpage), so you need to keep that in mind when driving, & if you don't want to register more than actual miles on your 914, since it affects resale value in some cases.
Try the Tires & Wheels topic, in the Originality & History forum for more info.